Monument of States EarthCache
Welcome!
The Monument of States is a fascinating structure showcasing geological diversity from across the United States. This EarthCache highlights dozens of distinct rock types, but we will focus on just three—sandstone, fossilized tree, and brain coral—and learn how to identify them through observation. Your challenge is to locate these rocks in the monument using the descriptions provided and determine which states contributed them.
Required Logging Tasks
To log this EarthCache, complete the following tasks:
- Based on the descriptions below, find a sandstone specimen within the monument. Describe its color, grain size, and texture, and identify which state contributed this rock.
- Locate a rock made of fossilized tree. Examine its surface texture and visible patterns. What features indicate that this was once wood? Which state donated it?
- Identify the brain coral fossil in the monument. Describe its surface texture and pattern. How does its structure suggest it was once a living organism? Which state contributed it?
- Take a photo of yourself (or a personal item) at the Monument of States to confirm your visit.
Earth Science Lesson
The Monument of States is not just a patriotic landmark; it also serves as an incredible geological showcase. Among the various rocks incorporated into the structure, we are going to focus on the unique characteristics of the three below:
Sandstone: The Rock of Time
How to Identify Sandstone:
- Color: Sandstone varies from red and brown to yellow and gray, depending on its mineral content. Red hues suggest iron oxide (rust), while lighter colors indicate quartz or feldspar dominance.
- Grain Size & Texture: Sandstone consists of sand-sized grains that feel gritty when touched. You may even be able to rub the surface and feel individual grains loosen.
- Formation: This rock forms from compacted sand over millions of years, often in riverbeds, deserts, or ocean shores. Over time, mineral-rich water cements the grains together, creating the solid rock you see today.
Where to Look:
A sandstone specimen is included in the Monument of States. By closely examining the grainy texture and coloration, you can locate it and determine which state it represents.
Fossilized Tree: Wood Turned to Stone
How to Identify Fossilized Wood:
- Surface Features: Look for structures resembling tree rings or grainy wood patterns. Unlike real wood, fossilized tree specimens are much heavier and do not burn.
- Texture: The surface may be smooth and polished or rough with mineral deposits. You should be able to observe mineral veins where the wood structure was replaced over time.
- Formation: Fossilized wood forms when trees are buried under sediment and deprived of oxygen. Over thousands to millions of years, groundwater rich in silica, calcite, or pyrite gradually replaces the organic material with minerals, preserving the original structure.
Where to Look:
A fossilized tree specimen is embedded in the Monument of States. Its distinct pattern will help you identify it. Once found, determine which state contributed it.
Brain Coral: The Fossil of a Seafloor Colony
How to Identify Brain Coral Fossils:
- Pattern & Shape: Brain coral fossils have a distinctive maze-like pattern, resembling the folds of a human brain. This is a hallmark of the coral’s skeletal structure.
- Texture: Unlike most other rocks, brain coral fossils have a porous, calcite-rich surface, often pitted with tiny holes where coral polyps once lived.
- Formation: Coral fossils form when coral reefs, made of calcium carbonate, become buried under sediment. Over thousands of years, the calcium in the coral structure turns into limestone, preserving the intricate design of the coral’s skeleton.
Where to Look:
A fossilized brain coral piece is included in the monument. Find this unique rock and determine which state donated it.
Final Thoughts
The Monument of States is more than just a collection of rocks—it tells a story of the geological history of the United States. Each rock has its own journey, from ancient sand dunes to prehistoric forests and coral reefs. By completing this EarthCache, you’ve explored the natural wonders locked within this monument!
References
- Geological Society of America (GSA) - EarthCache Guidelines.
- Information from the Monument of States plaques and historical markers.
- United States Geological Survey (USGS) resources on rock types and formation processes.
